Create a content page that will use the layout, defining any HTML to use for the
extension points in the layout, and specified by a layout:decorate/data-layout-decorate
processor at the root element of your page:

Get Thymeleaf to process your content page. The result will be the layout
template decorated by your content page, meaning that the content page will fill
out the layout's extension points, replace titles, and merge <head> items: